Fossil Salix polaris Wahlbg. in the Netherlands

From several places in the Netherlands fossil specimens of dwarf willows have been recorded, both from deposits of the last Glacial (Weichselian: Florschutz, 1930, 1936; Van der Vlerk and Florschutz, 1950, 1953) and of the penultimate Glacial (Saalian: Zagwijn and De Jong, 1960). As stated by Florschutz the arctic-montane species of Salix recorded with certainty are the following: S. herbacea, S. reticulata. S. retusa. The presence of S. polaris, however, had not yet been recorded with certainty (Van der Vlerk and Florschutz, 1950). In the present paper some specimens of this species will be described, which have been found lately near Hengelo, in a bed from the Weichselian Pleniglacial. This bed, consisting of about three metres of loam has been exposed among others in the pit of Rientjes, about 2 km due north of the town of Hengelo (Province of Overijssel). In this pit at the base of this bed, occurred in places a layer rich in plant debris, among which numerous leaves of arctic-montane species. The following species could be recorded: Salix herbacea L. (64 leaves), Salix reticulata L. (60 leaves), Salix polaris Wahlbg. (3, perhaps 5 leaves), Dryas octopetala L. (4 leaves), Betula nana L. (2 leaves). A radiocarbon dating of this material yielded the following result: 37 170 ± 840 y. BP; GRN-1763.